Design Strategy of Z-source Inverter for Utilization of Power Semiconductors with Extremely Low Short-circuit Capability

This paper proposes to utilize a feature of Z-source inverters (ZSIs) that does not require any withstanding capability of power semiconductor devices for short-circuit operations, owing to the inductors connected in the impedance-source circuits. The features of ZSIs enable the use of high performance power devices, such as SiC-MOSFETs and GaN-HEMTs which have extremely low on-resistance and high switching speed with no short-circuit capability. Therefore, the ZSIs can be expected to achieve higher power density and more improved efficiency. This paper discusses calculation methods which solve the maximum currents and voltages during and after load short-circuit operations in order to estimate the volume of passive components in the quasi-ZSIs in consideration of short-circuit faults. Results of some experimental verification clarified good accuracy of the proposed calculation, and also that the ZSIs enable to reduce power dissipation in the power devices during short-circuit operations, compared with voltage-source inverters. Further, this paper estimates the dependence of load short-circuit duration on the volume of passive components in the impedance-source in case of a fabricated quasi-Z-source converter. In case the load short-circuit duration is 10 μs, the volume of the inductors and capacitor are estimated to be 1.36 times and 1.08 times larger than that designed without considering short-circuit faults.